MINOR: Allow writing tombstone offsets for arbitrary partitions in the FileStreamSourceConnector

connect/file/src/main/java/org/apache/kafka/connect/file/FileStreamSourceConnector.java

@@ -117,18 +117,10 @@ public boolean alterOffsets(Map<String, String> connectorConfig, Map<Map<String,
         // This connector makes use of a single source partition at a time which represents the file that it is configured to read from.
         // However, there could also be source partitions from previous configurations of the connector.
         for (Map.Entry<Map<String, ?>, Map<String, ?>> partitionOffset : offsets.entrySet()) {
-            Map<String, ?> partition = partitionOffset.getKey();
-            if (partition == null) {
-                throw new ConnectException("Partition objects cannot be null");
-            }
-
-            if (!partition.containsKey(FILENAME_FIELD)) {
-                throw new ConnectException("Partition objects should contain the key '" + FILENAME_FIELD + "'");
-            }
-
             Map<String, ?> offset = partitionOffset.getValue();
-            // null offsets are allowed and represent a deletion of offsets for a partition
             if (offset == null) {
+                // We allow tombstones for anything; if there's garbage in the offsets for the connector, we don't
+                // want to prevent users from being able to clean it up using the REST API
                 continue;
             }
 
@@ -145,6 +137,15 @@ public boolean alterOffsets(Map<String, String> connectorConfig, Map<Map<String,
             if (offsetPosition < 0) {
                 throw new ConnectException("The value for the '" + POSITION_FIELD + "' key in the offset should be a non-negative value");
             }
+
+            Map<String, ?> partition = partitionOffset.getKey();
+            if (partition == null) {
+                throw new ConnectException("Partition objects cannot be null");
+            }
+
+            if (!partition.containsKey(FILENAME_FIELD)) {
+                throw new ConnectException("Partition objects should contain the key '" + FILENAME_FIELD + "'");
+            }
         }
 
         // Let the task check whether the actual value for the offset position is valid for the configured file on startup

connect/file/src/test/java/org/apache/kafka/connect/file/FileStreamSourceConnectorTest.java

@@ -227,4 +227,18 @@ public void testSuccessfulAlterOffsets() {
         assertTrue(connector.alterOffsets(sourceProperties, offsets));
         assertTrue(connector.alterOffsets(sourceProperties, new HashMap<>()));
     }
+
+    @Test
+    public void testAlterOffsetsTombstones() {
+        Function<Map<String, ?>, Boolean> alterOffsets = partition -> connector.alterOffsets(
+            sourceProperties,
+            Collections.singletonMap(partition, null)
+        );
+
+        assertTrue(alterOffsets.apply(null));
+        assertTrue(alterOffsets.apply(Collections.emptyMap()));
+        assertTrue(alterOffsets.apply(Collections.singletonMap(FILENAME_FIELD, FILENAME)));
+        assertTrue(alterOffsets.apply(Collections.singletonMap(FILENAME_FIELD, "/someotherfilename")));
+        assertTrue(alterOffsets.apply(Collections.singletonMap("garbage_partition_key", "garbage_partition_value")));
+    }
 }